Dual modulator displays have a first array of pixels that generates a controllable pattern of light at a second array of pixels. Examples of dual modulator displays are described in WO02/069030 (PCT/CA2002/000255) and WO03/077013 (PCT/CA2003/000350), both entitled HIGH DYNAMIC RANGE DISPLAY DEVICES. In some embodiments, image data specifying a desired image is supplied to a controller which operates the first array of pixels to yield a pattern of light at the second array of pixels. The pattern of light approximates the desired image. The controller operates the second array of pixels to modulate the pattern of light to yield an image that is closer to the desired image than the pattern of light. In some embodiments the first array of pixels has a lower resolution than the second array of pixels (i.e. there are more pixels in the second array of pixels than there are in the first array of pixels). The first array of pixels may comprise, for example, an array of individually-controllable light sources pixels of a spatial light modulator, or the like. The second array of pixels may comprise a reflective or transmissive spatial light modulator.
In some embodiments the first array of pixels comprises an array of light-emitting diodes (LEDs) and the second array of pixels comprises a liquid crystal display (LCD) panel.
A “dual modulator” display architecture can be suitable for use in high-end displays (some examples of high end displays are displays for viewing X-rays and other critical images; high-end cinema applications and the like). In such applications it is desirable to make the displayed image reproduce the desired image as closely as possible. In such applications, any perceptible deviation from the desired image is undesirable.
In a “perfect” dual modulator display the first set of pixels would have light outputs that are steplessly variable from zero to very bright and the second set of pixels would be steplessly controllable between transmitting zero light and passing all incident light. In the real world, the components practical for use as the first and second sets of pixels have limitations. For example, where the first or second set of pixels comprises pixels of an LCD (liquid crystal display) the pixels have a maximum transmission of less than 100%, a minimum transmission greater than 0%, and the transmission of each pixel is typically selectable from among a discrete set of values. Similarly, where the first set of pixels comprises an array of individually-controllable light sources (such as LEDs, for example) it is typical that the light sources have light outputs that can be adjusted in discrete steps up to some maximum value.
One problem is to determine how to control the first set of pixels so that the pattern of light on the second set of pixels will approximate the desired image in a way that can be corrected for by the second set of pixels to a high degree of accuracy.